Technical aspects of impurity control at JET : Status and future plans

Abstract

The salient feature of 1989-1990 operation of JET has been the use of beryllium as a first wall material. Technical and safety aspects of JET operation with beryllium are described. The use of beryllium has substantially improved the plasma purity and, as a consequence, a record fusion product n(D)T(i)tor(E) of 9 x 1.0 E20 s.keV/m3 has been achieved. Impurity influxes, however, prevent the achievement of higher plasma parameters and steady state conditions. A new divertor configuration has been proposed for JET with a view to studying impurity control, fuelling and exhaust, in conditions relevant for the next generation of machines. The latest design features a multi-coil configuration which gives substantive operational flexibility. A technical description of the major components of the divertor including the internal coils, the target plates and the pumping and fuelling systems is given.